Patent GB-220105-A (GB)
Title: A machine for shaping the teeth of bevel wheels by generating movements
IPC: B23F5/12
Filed: 1923-06-09
Abstract: 220,105. Barth, R. C. June 9, 1923. Gear-cutting. - In a machine for generating bevel gears, the blank is rotated about an adjustably fixed axis and the cutters which act alternately and represent one tooth of a crown wheel engaging the blank are first rolled in engagement with the blank to generate the tooth profile and then withdrawn and rolled reversely with the blank, which is finally indexed before the cutters re-engage to cut the next tooth. The main shaft 2 driven by a pulley 1 drives through bevel gearing 4 a shaft 5 carrying a pinion 6 which through a wheel 7, Fig. 3, and change gears 11 drives a countershaft 15 which carries a loose spur wheel 16 and a ratchet clutch member 27 driving a slidable clutch sleeve 26. A loose sleeve 14 driven in the opposite direction from the shaft 15 by a wheel 8 engaging the wheel 7, carries slidable clutch members 20, 21 engageable respectively with the spur wheel 16 and a loose wheel 25 on the sleeve 14. Rotation of the cutter head 19 is effected from the wheel 16 through a wheel 17, sliding one tooth clutch 44, change gearing 29, and worm gearing 32. Corresponding movement is also imparted to the blank spindle 18 from the gear 17 through a wheel 33, change gears 35, bevel gearing 38, shaft 40, bevel gearing 42 and shaft 43. The actuation of the forward and return rolling movements and the indexing movement of the blank is controlled automatically by means of the clutch sleeves 26, 20, 21. During the forward .generating movement the clutches are in the position shown in Fig. 7 and the blank and cutter head are slowly rotated from the wheel 16, which is being driven at the speed of the shaft 15. At the end of the movement the clutch 26 is disengaged and the clutch 20 engaged so that the wheel 16 is now reversely driven at the high speed of the tubular member 14 for the backward roll. On completion of the backward movement the one-tooth clutch is disengaged from the wheel 17 which thereupon rotates one revolution to index the blanl: while the movement of the cutter head is interrupted. After completing the indexing movement the blank and tool are rolled forward at the high speed to take up backlash in the gear trains. This is effected by disengaging the clutch 20 and engaging the clutch 21 with the wheel 25 from which movement is transmitted through wheels 45 and 33 on a countershaft 34 to the wheel 17. The clutch 26 is also in engagement but the wheel 16 is permitted to overrun the slow feed by means of the ratchet clutch 27. Finally the clutch 21 is disengaged so that the clutches are in the positions shown in Fig. 7 and the next forward roll commences. The clutches are automatically controlled by means of a non-rotating nut 47 which is mounted on a lead screw 46 provided on the shaft 28 and which carries extensions 50 - - 52 for operating the clutches as shown in Fig. 6. During the generating movement the nut 47 moves to the left until the extension 50 actuates the connected clutch-forks 53, 54 to interrupt the slow generating roll and commence the fast return roll. The nut 47 now moves to the right. Towards the end of the movement the clutch 44 is withdrawn to permit indexing. The clutch fork 55 is then operated to engage the clutch 21 for the high-speed movement to take up back-lash. At the same time the clutch forks 53, 54 are moved to the position shown in Fig. 7. Finally the clutch fork 55 is operated by the extension 51 to withdraw the clutch 21 and start the slow generating movement. The tools 73, 74 are reciprocated from the main shaft 2 through gears 65, 66, shaft 69, and gears 71, 72, and in order to lift the tool 74 from the work on the return stroke the shaft 69 has an eccentric portion 76 engaging a roller 78 on a lever 79 connected to a rail 82 engaged by a roller 86 on the swinging tool-holder 87. At the commencement of the return stroke the lever 79 is actuated by its eccentric to depress the rail 82 and so lift the tool away from the work. The other tool is similarly actuated from a second eccentric. On completion of the forward generating movement the tools are held entirely clear of the work during the return roll. This is effected in the case of the cutter 74 by means of a pawl 106 interconnected with the clutch 20 and actuating a loose ring 95 on the cutter head to shift a sliding rod 100 connected to the rail operating lever 79. When the clutch 20 is again disengaged for a forward roll the pawl 106 is reversely operated to restore the cutters to their normal position.